182 THE LIMITATIONS OF SCIENCE 



explanation of the Michelson-Morley effect and of 

 some others, but this loss is not overwhelming and we 

 can afford to wait for an explanation until a future 

 time. 



I am the more willing to take this attitude, because 

 I can see no means of applying the Principle of Rela- 

 tivity to the test of experience. As we have seen, the 

 velocity of light in any material medium is a variable 

 and can be no more trusted than the velocity of sound. 



Perhaps this illustration may make my meaning 

 clearer. Suppose a race of men to exist who are blind 

 and have no knowledge of electro-magnetic radiation, 

 but who wish to measure the lengths of moving bodies. 

 They will undoubtedly be compelled to get this in- 

 formation and that of the synchronism of clocks by 

 sound signals. It is evident that observations car- 

 ried out under conditions similar to those imposed by 

 Professor Einstein would indicate that the length of 

 a moving body underwent changes. And while they 

 could make corrections for some of the effects, because 

 sound waves are largely affected by the motion of 

 media and of sonorous bodies, yet they would undoubt- 

 edly come to the conclusion that the dimensions of a 

 moving body depended to some extent on its motion. 

 Now, if we should bestow sight on one of these men, he 

 would be able to correct their measurements; as he 

 could by his immensely more rapid light signals gain a 

 much more nearly instantaneous value for synchronism. 



